Comments for Forensic Question: Presence of Semen

Phosphatesmo KM is a test that is used for the presumptive idenfication of semen in stains. It is indicative for the presence of an enzyme (acid phosphatase) that is present in semen in relatively high concentrations. In the presence of acid phosphatase, the test paper develops violet stains on the white test paper. This test does not show the actual presence of sperm cells, it only detects the enzyme present in sperm fluid.

Method of application:

The carrier is normally subjected to a macroscopic examination for suspicious spots. Textiles generally assume boardlike consistency and yield a bluish, white or yellow fluorescence under a longwave UV lamp. Since this fluorescence is often difficult to see due to the fluorescence of optical brighteners from laundry detergents, the 450 nm band of the Polilight in combination with orange goggles or 530 nm interference filters is a much better method.

Specifity:

Phosphatesmo KM is specific for acid phosphatase. Acide Control tests with saliva, mucus or female genital secretions give negative results. The reaction is not a suitable substitute for the microscopic determination of live spermatozoa.

PSA test:

This test detects the presence of prostate specific antigen. Again it does not detect the actual sperm cells but just the secretion fluid that comes with the ejaculation.

The disadvantage of the methods is that they also test positive with different vegetables, urine and other substances. Therefore the only real test to detect sperm is the use of a microscopic test to look for actual sperm cells.